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Philosophy of Spiritual Activity
GA 4

VII. Are There Limits to Knowledge?

WE have established that the elements for the explanation of reality are to be taken from the two spheres of perception and thinking. It is due, as we have seen, to our organization that the full totality of reality, including our own selves as subjects, appears at first as a duality. Knowledge overcomes this duality by fusing the two elements of reality, the percept and the concept gained by thinking, into the complete thing. Let us call the manner in which the world presents itself to us, before by means of knowledge it has taken on its true nature, “the world of appearance,” in distinction from the unified whole composed of percept and concept. We can then say: The world is given to us as a duality, and knowledge transforms it into a unity. A philosophy which starts from this basic principle may be called a Monistic philosophy, or Monism. Opposed to this is the theory of two worlds, or Dualism. The latter does not indeed assume that there are two sides of a single reality, which are kept apart merely by our organization, but that there are two worlds absolutely distinct from one another. It then tries to find in one of these two worlds the principles of explanation for the other.

Dualism rests on a false conception of what we call knowledge. It divides the whole of existence into two spheres, each of which has its own laws, and it leaves these two worlds standing opposite and outside one another.

It is from a Dualism such as this that there arises the distinction between the object of perception and the thing-in-itself, which Kant introduced into science, and which, to the present day, we have not succeeded in expelling. According to our interpretation, it is due to the nature of our spiritual organization that a particular thing can be given to us only as a percept. Thinking then overcomes this particularity by assigning to each percept its legitimate place in the world as a whole. As long as we determine the separated parts of the cosmos as percepts, we are simply following, in this sorting out, a law of our subjectivity. If, however, we regard all percepts, taken together, merely as one part, and contrast with this a second part, viz., the things-in-themselves, then our philosophy is building castles in the air. We are then engaged in mere playing with concepts. We construct an artificial opposition, but we can gain no content for the second of these opposites, for such a content for a particular thing can be gathered only from perception.

Every kind of existence which is assumed outside the realm of percept and concept must be relegated to the sphere of unjustified hypotheses. To this category belongs the “thing-in-itself.” It is quite natural that a Dualistic thinker should be unable to find the connection between the world-principle which he hypothetically assumes and the things given in experience. For the hypothetical world-principle itself a content can be found only by borrowing it from the world of experience and shutting one's eyes to the fact of the borrowing. Otherwise it remains an empty concept, a non-concept which has only the form of a concept. In this case the Dualistic thinker generally asserts that the content of this concept is inaccessible to our knowledge. We can know only that such a content exists, but not what it is. In either case it is impossible to overcome Dualism. Even though one were to import a few abstract elements from the world of experience into the concept of the thing-in-itself, it would still remain impossible to reduce the rich concrete life of experience to those few qualities which are, after all, themselves taken from perception. Du Bois-Reymond lays it down that the imperceptible atoms of matter produce sensation and feeling by means of their position and motion, and then comes to the conclusion that we can never find a satisfactory explanation of how matter and motion produce sensation and feeling, for “it is absolutely and for ever unintelligible that it should be other than indifferent to a number of atoms of carbon, hydrogen, and nitrogen, etc., how they lie and move, how they lay and moved, or how they will lie and will move. It .is in no way intelligible how consciousness can come into existence through their interaction.” This conclusion is characteristic of the tendency of this whole trend of thought. Position and motion are abstracted from the rich world of percepts. They are then transferred to the fictitious world of atoms. And then astonishment arises that life cannot be evolved out of this self-made principle borrowed from the world of percepts.

That the Dualist, working as he does with a completely empty concept of the thing-in-itself, can reach no explanation of the world, follows already from the very definition of his principle which has been given above.

In any case, the Dualist finds it necessary to set impassable barriers to our faculty of knowledge. The follower of a Monistic world-conception knows that all he needs to explain any given phenomenon in the world is to be found within this world itself. What prevents him from reaching it can be only contingent limitations in space and time, or defects of his organization, i.e., not of human organization in general, but only of his own particular one.

It follows from the concept of knowledge, as defined by us, that there can be no talk of limits of knowledge. Knowledge is not a concern of the universe in general, but one which men must settle for themselves. Things claim no explanation. They exist and act on one another according to laws which thinking can discover. They exist in indivisible unity with these laws. Our Egohood confronts them, grasping at first only what we have called percepts. However, within our Egohood we find the power to discover also the other part of reality. Only when the I has combined for itself the two elements of reality which are indivisibly bound up with one another in the world, is our thirst for knowledge stilled. The I has then again attained reality.

The presuppositions for the arising of the act of knowledge thus exist through and for the I. It is the I which sets itself the problems of knowledge. It takes them from thinking, an element which in itself is absolutely clear and transparent. If we set ourselves questions which, we cannot answer, it must be because the content of the questions is not in all respects clear and distinct. It is not the world which sets questions to us, but we who set them.

I can imagine that it would be quite impossible for me to answer a question which I happened to find written down somewhere, without knowing the sphere from which the content of the question was taken.

In knowledge we are concerned with questions which arise for us through the fact that a sphere of percepts, conditioned by time, space, and our subjective organization, stands over against a sphere of concepts pointing to the totality of the universe. My task consists in reconciling these two spheres, with both of which I am well acquainted. There is no room here for speaking of limits of knowledge. It may be that, at a particular moment, this or that remains unexplained because, through our place in life, we are prevented from perceiving the things involved. What is not found to-day, however, may be found to-morrow. The limits due to these causes are only transitory, and must be overcome by the progress of perception and thinking.

Dualism makes the mistake of transferring the opposition of object and subject, which has meaning only within the perceptual realm, to purely fictitious entities outside this realm. Now the distinct and separate things within the perceptual field remain separated only so long as the perceiver refrains from thinking. For thinking cancels all separation and reveals it as due to purely subjective conditions. The Dualist, therefore, transfers to entities behind the percepts determinations which, by themselves, have no absolute, but only relative, validity. He thus divides the two factors concerned in the process of knowledge, viz., percept and concept, into four: (1) the object in itself; (2) the percept which the subject has of the object; (3) the subject; (4) the concept which relates the percept to the object in itself. The relation between subject and object is “real”; the subject is really (dynamically) influenced by the object. This real process is supposed not to appear in consciousness. But it is said to evoke in the subject a response to the stimulation from the object. The result of this response is said to be the percept. This, at length, is supposed to appear in consciousness. The object is thought to have an objective (independent of the subject) reality, the percept a subjective reality. This subjective reality is said to be referred by the subject to the object. This latter reference is called an ideal one. Dualism thus divides the process of knowledge into two parts. The one part, viz., the production of the perceptual object by the thing-in-itself, he conceives of as taking place outside consciousness, whereas the other, the combination of percept with concept and the letter's reference to the thing-in-itself, takes place, according to him, within consciousness.

With such presuppositions, it is clear why the Dualist regards his concepts merely as subjective representatives of what lies before his consciousness. The objectively real process in the subject by means of which the percept is produced, and still more the objective relations between, things-in-themselves, remain for the Dualist inaccessible to direct knowledge. According to him, man can get only conceptual representatives of the objectively real. The bond of unity of things which connects them with one another, and also objectively with the individual spirit (as things-in-themselves) of each of us, lies beyond our consciousness in a Being in itself of whom, once more, we may have in our consciousness merely a conceptual representative.

The Dualist believes that the whole world would be dissolved into a mere abstract scheme of concepts, did he not posit real connections beside the conceptual ones. In other words, the ideal principles which thinking discovers seem too airy for the Dualist, and he seeks, in addition, “real principles” with which to support them.

Let us examine these real principles a little more closely. The naive man (Naive Realist) regards the objects of external experience as realities. The fact that his hands can grasp, and his eyes see these objects, is for him sufficient proof of their reality. “Nothing exists that cannot be perceived” is, in fact, the first axiom of the naive man; and it is held to be equally valid in its converse: “Everything which can be perceived exists.” The best proof for this assertion is the naive man's belief in immortality and in ghosts. He thinks of the soul as a fine kind of sensible matter which, in special circumstances, may actually become visible to the ordinary man (naive belief in ghosts).

In contrast with this, his real world, the Naive Realist regards everything else, especially the world of Ideas, as unreal, or “merely ideal.” What we add to objects by thinking is merely thoughts about the objects. Thought adds nothing real to the percept.

But it is not only with reference to the existence of things that the naive man regards sense-perception as the sole proof of reality, but also with reference to the occurrences (processes). A thing, according to him, can act on another only when a force actually present to perception issues from the one and seizes upon the other. The older physicists thought that very. fine kinds of substances emanate from the objects and penetrate through the sense-organs into the soul. The actual seeing of these substances is impossible only because of the coarseness of our sense-organs relatively to the fineness of these substances. In principle, the reason for attributing reality to these substances was the same as that for attributing it to the objects of the sensible world, viz., their form of existence, which was conceived to be analogous to that of sense reality.

The self-contained character of that which is of the nature of thought is not regarded by the naive mind as real in the same sense. An object conceived “merely in Idea” is regarded as a chimera until sense-perception can furnish conviction of its reality. In short, the naive man demands, in addition to the ideal evidence of his thinking, the real evidence of his senses. In this need of the naive man lies the ground for the origin of primitive forms of the belief in revelation. The God who is given through thinking remains always a God merely “thought.” The naive consciousness demands that God should manifest Himself in ways accessible to sense-perception. God must appear in the flesh, and little value is attached to the testimony of thinking, but only to the divine nature being proved by the changing of water into wine in a way which can be testified by the senses.

Even knowledge itself is conceived by the naive man as a process analogous to sense-perception. Things, it is thought, make an impression on the soul, or send out images which enter through our senses, etc.

What the naive man can perceive with his senses he regards as real, and what he cannot thus perceive (God, soul, knowledge, etc.) he regards as analogous to what he perceives.

On the basis of Naive Realism, science can consist only in an exact description of the content of perception. Concepts are only means to this end. They exist to provide ideal counterparts of percepts. For the things themselves they do not matter. For the Naive Realist only the individual tulips, which we see or can see, are real. The Idea of the tulip is to him an abstraction, the unreal thought-picture which the soul combines for itself out of the characteristics common to all tulips.

Naive Realism, with its fundamental principle of the reality of all perceived things, contradicts experience, which teaches us that the content of percepts is of a transitory nature. The tulip I see is real to-day; in a year it will have vanished into nothingness. What persists is the species “tulip.” This species is, however, for the Naive Realist “merely” an Idea, not a reality. Thus this theory of the world finds itself in the position of seeing its realities arise and perish, while that which, by contrast with its realities, it regards as unreal, endures. Hence Naive Realism is compelled to acknowledge the existence of something ideal by the side of percepts. It must include within itself entities which cannot be perceived by the senses. In admitting them, it escapes contradicting itself by conceiving their existence as analogous to that of objects of sense. Such hypothetical realities are the invisible forces by means of which the objects of sense-perception act on one another. Another such reality is heredity, the effects of which survive the individual, and which is the reason why from the individual a new being develops which is similar to it, and by means of which the species is maintained. The life-principle permeating the organic body, the soul, is another such reality which the naive mind is always found conceiving in analogy to sense-realities. And, lastly, the Divine Being, as conceived by the naive mind, is a reality of this kind. This Being is thought of as acting in a manner exactly corresponding to that which we can perceive in man himself, i.e., the Deity is conceived anthropomorphically.

Modern Physics traces sensations back to processes of the smallest particles of bodies and of an infinitely fine substance, called ether, or the like. What we experience, e.g., as warmth is a movement of the parts of a body which causes the warmth in the space occupied by that body. Here again something imperceptible is conceived on the analogy of what is perceptible. Thus, the perceptible analogon to the concept “body” is, say, the interior of a room, shut in on all sides, in which elastic balls are moving in all directions, impinging one on another, bouncing on and off the walls, etc.

Without such assumptions the world of Naive Realism would collapse into a disconnected chaos of percepts, without mutual relations, and having no unity within itself. It is clear, however, that Naive Realism can make these assumptions only by an inconsistency. If it would remain true to its fundamental principle, that only what is perceived is real, then it ought not to assume a reality where it perceives nothing. The imperceptible forces of which perceptible things are the bearers are, in fact, illegitimate hypotheses from the standpoint of Naive Realism. And because Naive Realism knows no other realities, it invests its hypothetical forces with perceptual content. It thus transfers a form of existence (the perceptible existence) to a sphere where the only means of making any assertion concerning such existence, viz., sense-perception, is lacking.

This self-contradictory theory leads to Metaphysical Realism. The latter constructs, beside the perceptible reality, an imperceptible one which it conceives on the analogy of the former. Metaphysical Realism is, therefore, of necessity Dualistic.

Wherever the Metaphysical Realist observes a relation between perceptible things (mutual approach through movement, the entrance of an object into consciousness, etc.), there he posits a reality. However, the relation which he notices can only be expressed by means of thinking, but not perceived. The ideal relation is thereupon arbitrarily imagined as something perceptible. Thus, according to this theory, the real world is composed of the objects of perception which are in ceaseless flux, arising and disappearing, and of imperceptible forces by which the perceptible objects are produced, and which are permanent.

Metaphysical Realism is a heterogeneous mixture of Naive Realism and Idealism. Its hypothetical forces are imperceptible entities endowed with the qualities proper to percepts. The Metaphysical Realist has made up his mind to acknowledge, in addition to the sphere for the existence of which he has an instrument of knowledge in sense-perception, the existence of another sphere for which this instrument fails, and which can be known only by means of thinking. But he cannot make up his mind at the same time to acknowledge that the mode of existence which thinking reveals, viz., the concept (or Idea), has equal rights with percepts. If we are to avoid the contradiction of imperceptible percepts, we must admit that, for us, the relations which thinking traces between percepts can have no other mode of existence than that of concepts. If one rejects the untenable part of Metaphysical Realism, there remains the concept of the world as the sum of percepts and their conceptual (ideal) relations. Metaphysical Realism, then, merges itself in a view of the world according to which the principle of perceptibility holds for percepts, and that of conceivability for the relations between the percepts. This view of the world has no room, in addition to the perceptual and conceptual worlds, for a third sphere, in which both principles, the so-called “real” principle and the “ideal” principle, are simultaneously valid.

When the Metaphysical Realist asserts that, beside the ideal relation between the perceived object and the perceiving subject, there must exist a real relation between the “thing-in-itself” of the percept and the “thing-in-itself” of the perceptible subject (i.e., of the so-called individual spirit), he is basing his assertion on the false assumption of a real process, analogous to the processes in the sense-world, but imperceptible. Further, when the Metaphysical Realist asserts that we enter into a conscious ideal relation to our world of percepts, but that to the real world we can have only a dynamic (force) relation, he repeats the mistake we have already criticized. One can talk of a dynamic relation only within the world of percepts (in the sphere of the sense of touch), but not outside that world.

Let us call the view which we have just characterized, and into which Metaphysical Realism merges when it discards its contradictory elements, Monism, because it combines one-sided Realism and Idealism into a higher unity.

For Naive Realism, the real world is an aggregate of objects of perception; for Metaphysical Realism, reality belongs not only to percepts but also to imperceptible forces; Monism replaces forces by ideal connections which are supplied by thinking. Such connections are the Laws of Nature. A Law of Nature is nothing but the conceptual expression for the connection of certain percepts.

Monism is never called upon to ask for any other principles of explanation for reality than percepts and concepts. It knows that in the whole range of the real there is no occasion for this question. In the perceptual world, as it lies before perception, it sees one-half of reality: in the union of this world with the world of concepts it finds full reality. The Metaphysical Realist may reply to the adherent of Monism that, for our organization, our knowledge may be complete in itself, that no part may be lacking; but we do not know how the world is mirrored in an Intelligence organized differently from our own. To this the Monist will reply: Maybe there are Intelligences other than human; if their percepts are different from ours, all that concerns me is what reaches me from them through perception and concept. Through my perceiving, i.e., through this specifically human mode of perceiving, I, as subject, am confronted with the object. The connection of things is thereby broken. The subject restores this connection by means of thinking. In doing so it re-inserts itself into the context of the world as a whole. As it is only through the subject that the whole appears rent in two at the place between our percept and concept, the reunion of those two factors gives us true knowledge. For beings with a different perceptual world (e.g., if they had twice our number of sense-organs) the nexus would appear broken in another place, and the reconstruction would accordingly have to take a form specific for such beings. The question concerning the limits of knowledge exists only for Naive and Metaphysical Realism, both of which see in the contents of the soul only an ideal representative of the real world. For, to these theories, whatever falls outside the subject is something absolute, a self-contained whole, and the subject's mental content is a picture thereof which is wholly external to this absolute. The completeness of knowledge depends on the greater or lesser degree of resemblance between the picture and the absolute object. A being with fewer senses than man will perceive less of the world, one with more senses will perceive more. The former's knowledge will, therefore, be less complete than the latter's.

For Monism, the situation is different. The form in which the connection of the world appears to be rent asunder into subject and object depends on the organization of the perceiving being. The object is no absolute one but merely a relative one in reference to this particular subject. The bridging of the opposition, therefore, can again take place only in the quite specific way which is characteristic of the human subject. As soon as the I, which in perception is separated from the world, again reinserts itself into the world-nexus by thinking investigation, all further questioning ceases, having been but a consequence of the separation.

A differently constituted being would have a differently-constituted knowledge. Our own knowledge, suffices to answer the questions put by our own nature.

Metaphysical Realism must ask: How are our percepts given? What is it that affects the subject?

Monism holds that percepts are determined through the subject. But, in thinking, the subject has, at the same time, the instrument for canceling this self-produced determination.

The Metaphysical Realist is faced by a further difficulty when he seeks to explain the similarity of the world-pictures of different human individuals. He has to ask himself: How is it that my picture of the world, built up out of subjectively determined percepts and out of concepts, turns out to be like that which another individual is also building up out of these same two subjective factors? How, in any case, can I draw conclusions from my own subjective picture of the world on that of another human being? The Metaphysical Realist thinks he can infer the similarity of the subjective world-pictures of different human beings from their ability to get on with one another in practical life. From this similarity of world-pictures he then infers the likeness to one another of the “Individual Spirits” underlying the single human perceiving subjects, or the “I-in-itself” underlying the subjects.

We have here an inference from a sum of effects to the character of the underlying causes. We believe we can, out of a sufficiently large number of instances, recognize the case sufficiently to know how the inferred causes will act in other instances. Such an inference is called an inductive inference. We shall be obliged to modify its results, if further observation yields some unexpected element, because the character of our conclusion is, after all, determined only by the particular shape of our actual observations. The Metaphysical Realist asserts that this knowledge of causes, though relative, is quite sufficient for practical life.

Inductive inference is the methodical basis of modern Metaphysical Realism. At one time it was thought that out of concepts we could evolve something that is no longer a concept. It was thought that the metaphysical real Beings, which Metaphysical Realism after all requires, could be known by means of concepts. This kind of philosophizing is now out of date. Instead it is thought that from a sufficiently large number of perceptual facts one can infer the character of the thing-in-itself which underlies these facts. Formerly it was from concepts, now it is from percepts, that people seek to evolve the metaphysical. Since one has concepts before oneself in transparent clearness, it was thought that one might deduce from them the metaphysical with absolute certainty. Percepts are not given with the same transparent clearness. Each subsequent one is a little different from others of the same kind which preceded it. Actually, therefore, anything inferred from past percepts is somewhat modified by each subsequent percept. The character of the metaphysical thus obtained can, therefore, be only relatively true, for it is open to correction by further instances. The character of von Hartmann's Metaphysics is determined by this methodological principle. The motto on the title-page of his first important book is, “Speculative results gained by the inductive method of Natural Science.”

The form which the Metaphysical Realist at the present day gives to his things-in-themselves is obtained by inductive inferences. Through considerations of the process of knowledge he is convinced of the existence of an objectively-real world-nexus, over and above the “subjective” world-nexus which we know by means of percepts and concepts. The nature of this reality he thinks he can determine by inductive inferences from his percepts.


The unprejudiced study of experience, in perceiving and conceiving, such as we have attempted to describe it in the preceding chapter, is liable to be disturbed again and again by certain representations which spring from the soil of natural science. Thus, taking one's stand on science, one says that the eye perceives in the spectrum colours from red to violet. But beyond violet there lie forces within the compass of the spectrum to which corresponds, not a colour perceived by the eye, but a chemical effect. Similarly, beyond the activity of red, there are rays which have only heat effects. These and similar phenomena lead, on reflection, to the view that the range of man's perceptual world is defined by the range of his senses, and that he would have before himself a very different world if he had additional, or altogether different, senses. Those who like to indulge in far-roaming fancies for which the brilliant discoveries of recent scientific research in this direction provide a highly tempting occasion, may well be led to confess that nothing enters the field of man's observation except what-can affect his senses, as these have been determined by his organization. Man has no right to regard his percepts, limited as these are by his organization, as in any way a standard to which reality must conform. Every new sense would confront him with a different picture of reality. Within its proper limits, this is a wholly justified view. But if anyone lets himself be confused by this view in the unprejudiced study of the relation of percept and concept, as set forth in these chapters, he blocks the path for himself to a knowledge of man and the world which is rooted in reality. The experiencing of the essential nature of thinking, i.e., the active appropriation of the world of concepts, is something wholly different from the experiencing of a perceptible object through the senses. Whatever additional senses man might have, not one would give him reality, if his thinking did not permeate with concepts whatever he perceived by means of such a sense. Every sense, whatever its kind, provided only it is thus permeated, enables man to live amidst the real. The fancy-picture of other perceptual worlds, made possible by other senses, has nothing to do with the problem of how man stands in the midst of reality. We must clearly understand that every perceptual picture of the world owes its form to the organization of the perceiving being, but that only that perceptual picture which has been thoroughly permeated by a thinking investigation leads us into reality. Fanciful speculations concerning how different the world would appear to other than human senses, can give us no occasion to seek for knowledge of man's relation to the world; but only the recognition that every percept presents only a part of the reality it contains, and that, consequently, it leads us away from its own proper reality. This recognition is supplemented by the further one that thinking leads us into the part of reality which the percept conceals in itself. Another difficulty in the way of the unprejudiced study of the relation we have here described, between percept and concept as elaborated by thinking, may be met with, when in the field of physical experience the necessity arises of speaking, not of immediately perceptible elements, but of non-perceptible magnitudes, such as, e.g., lines of electric or magnetic force.

It may seem as if the elements of reality of which physicists speak, had no connection either with what is perceptible, or with the concepts which active thinking has elaborated. Yet such a view would rest on self-deception. The main point is that all the results of physical research, except illegitimate hypotheses which ought to be excluded, have been gained through perceiving and conceiving. Elements which are seemingly non-perceptible, are placed by the physicists' sound instinct for knowledge into the field in which percepts lie, and they are thought of in concepts which are commonly applied in this field. The magnitudes in a field of electric or magnetic force are reached, in their essence, by no other cognitive process that the one which connects percept and concept. — An increase or a modification of human senses would yield a different perceptual picture, an enrichment or a modification of human experience. But genuine knowledge could be gained also concerning this new experience only through the mutual co-operation of concept and percept. The deepening of knowledge depends on the powers of intuition which express themselves in thinking (see p. 70). This Intuition may, in the living experience which expresses itself in thinking, dive either into deeper or shallower levels of reality. An expansion of the perceptual picture may supply stimuli for, and thus indirectly promote, this diving of intuition. But this diving into the depth, through which we attain reality, ought never to be confused with the contrast between a wider and a narrower perceptual picture, which always contains only half of reality, as that is conditioned by the structure of the cognizing organization. He who does not lose himself in abstractions will understand how for a knowledge of human nature the fact is relevant, that physics must infer the existence, in the field of percepts, of elements for which no sense is tuned as for colour or sound. Human nature, taken concretely, is determined not only by what, in virtue of his organization, man faces as immediate percept, but also by all else which he excludes from this immediate percept. Just as life needs unconscious sleep alongside of conscious waking experience, so man's experience of himself needs over and above the range of his sense-perception another sphere — and a much bigger one — of non-perceptible elements belonging to the same field from which the percepts of the senses come. All this was laid down by implication in the original argument of this book. The author adds the present amplification of the argument, because he has found by experience that some readers have not read attentively enough.

It is to be remembered, too, that the Idea of percept, developed in this book, is not to be confused with the Idea of external sense-percept which is but a special instance of the other. The reader will gather from what has preceded, but even more from what will be expounded later, that everything is here taken as “percept,” which sensuously or spiritually approaches man, so long as it has not yet been grasped by the actively elaborated concept. No “senses,” as we ordinarily understand the term, are necessary in order to have percepts of a physical or spiritual kind. It may be urged that this extension of ordinary usage is illegitimate. But the extension is absolutely necessary, unless we are to be prevented by the current sense of a word from enlarging our knowledge of certain realms of facts. He who uses “percept” only as meaning “sense-percept,” will never arrive at a concept fit for the purposes of knowledge even regarding sense-percept. It is sometimes necessary to enlarge a concept in order that it may get its appropriate meaning within a narrower field. Again, it is at times necessary to add to the original content of a concept, in order that the original concept may be justified or, perhaps, readjusted. Thus we find it said here in this book (p. 80): “A representation is an individualized concept.” It has been objected that this is an unusual use of the word. But this use is necessary if we are to find out what a representation really is. How can we expect any progress in knowledge, if everyone who finds himself compelled to readjust concepts, is to be met by the objection: “This is an unusual use of the word”?